The present invention relates to fluid pumping from subsurface wells and relates, in particular, to pumping high viscosity fluids such as viscous crude oils using a reciprocating rod string.
In prior art systems, pumping viscous fluids through a production tube string by means of a reciprocating rod string driving a recriprocating pump, friction between the rod string and the viscous fluid has created serious problems.
For example, extra power is required to drive the reciprocating rod through the viscous fluid.
This difficulty leads frequently to buckled or bent rods, tube damage and in severe cases parting of the rod string.
The highly viscous fluids also create a flotation effect tending to buoy the rod resulting in uneven cyclic power requirements putting an undesirable strain of the gear box of the rod driving mechanism. This occurrence frequently leads to premature failure of a very expensive gear train.
This excessive friction and flotation effect operates to slow the pumping speed reducing the flow of product.